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Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada)
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Date: Mon, 14 Mar 2005 23:39:35 GMT
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Xref: g2news1.google.com comp.lang.ada:9410 comp.lang.c++:45711
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Date: 2005-03-14T23:39:35+00:00
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Robert A Duff wrote:
> Because the "<" (or Hash) needs to know the internals of the thing.

It may be possible to order the objects through information
available from public accessors, so this is false.

> In other words, at the point where you declare a type, you have to think
> ahead: this type might want to live inside one of those containers, so
> I'd better define the necessary operations.

False, as per above. In fact, the ordered containers can be instantiated
with order functions, so there need not be a single unique ordering for
a given type.

For example, any string type has a public way of delivering up the
characters it contains. That lets you define string containers which
hold their strings in alphabetical order, in case-insensitive order,
or even in pig-latin order if you want. None of this requires the
string implementor to anticipate such ordering requirements.